This invention relates generally to the attachment of pavement markers to a paved roadway surface, and, more particularly, to the attachment of raised pavement markers to a paved surface by melting an adhesive pad using a pyrotechnic patty.
Modern roadway construction includes, as a safety feature, the installation of raised pavement markers 10, shown in FIG. 1, at selected intervals along the lane-divider lines of a surfaced roadway. The pavement markers may have a variety of shapes and sizes, depending upon their location and desired effect. One common lane or pavement marker, the "Bott's Dot," is a circular ceramic disk having a generally flat bottom surface and a domed upper surface. The diameter of the disk is about 4 inches and the height of the disk at the crown of the domed surface is about 3/4 inch. Alternatively, the pavement maker may have a square or rectangular shape and may include a retro reflective plastic covering.
Several techniques are used for attaching the pavement markers 10 to a paved surface 12. Initially, epoxy was the favored adhesive for attaching the markers to the roadway surface. However, epoxy is slow to cure, requires closure of the affected lanes for an extended time period, and is subject to failure if mixed in an improper proportion. A technique that currently is favored uses bitumen 14, a tar-like substance that solidifies quickly and has high shear strength, especially at mid to low temperatures, as an adhesive for attaching the markers to the roadway surface.
Bitumen is specified as a mixture of about 25-35% by weight of asphalt and about 65-75% by weight of calcium carbonate. To attach the pavement marker 10, a small puddle of molten bitumen 14 is poured onto the roadway surface 12 and the pavement marker is placed in the puddle. The bitumen is allowed to cool and solidify, to form a strong bond between the pavement marker and the roadway surface. To be applied in its molten state, the bitumen must be heated to a temperature above 204.degree. C. which creates operational and worker safety problems. Often, a propane-heated tank of molten bitumen must be towed to the attachment site and installation might be further delayed since approximately two hours is required for a propane heater to heat the bitumen to its melting point. Also, the bitumen is messy, tends to foul automated equipment, and often solidifies in delivery hoses if the process is interrupted.
Accordingly, there is a need for an attachment device and method that can attach a raised pavement marker to a roadway surface in a relatively safe, efficient, and economical manner, and that may be suitable for incorporation in an automatic attachment system. The present invention satisfies this need.